The second of these laws can expressed as the derivative with respective to time of the areal velocity is equal to zero. The third of these laws states that the square of the orbital period is directly proportional to the cube of the semi-major axis. The second of them, often expressed as "equal area over equal time", is a direct consequence of the conservation of angular momentum. For 10 points, name this group of three 
The second of these laws can expressed as the derivative with respective to time of the areal velocity is equal to zero. The third of these laws states that the square of the orbital period is directly proportional to the cube of the semi-major axis. The second of them, often expressed as "equal area over equal time", is a direct consequence of the conservation of angular momentum. For 10 points, name this group of three astronomical laws, the first of which states that the orbit of a planet around the sun takes the form of an ellipse.
The second of these laws can expressed as the derivative with respective to time of the areal velocity is equal to zero.
{Kepler’s} laws